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Semaphore.h
1 /* mbed Microcontroller Library
2  * Copyright (c) 2006-2019 ARM Limited
3  * SPDX-License-Identifier: MIT
4  *
5  * Permission is hereby granted, free of charge, to any person obtaining a copy
6  * of this software and associated documentation files (the "Software"), to deal
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9  * copies of the Software, and to permit persons to whom the Software is
10  * furnished to do so, subject to the following conditions:
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12  * The above copyright notice and this permission notice shall be included in
13  * all copies or substantial portions of the Software.
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15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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21  * SOFTWARE.
22  */
23 #ifndef SEMAPHORE_H
24 #define SEMAPHORE_H
25 
26 #include <stdint.h>
27 #include <chrono>
28 #include "rtos/mbed_rtos_types.h"
29 #include "rtos/internal/mbed_rtos1_types.h"
30 #include "rtos/internal/mbed_rtos_storage.h"
31 #include "rtos/Kernel.h"
32 #include "platform/mbed_toolchain.h"
33 #include "platform/NonCopyable.h"
34 
35 namespace rtos {
36 /** \addtogroup rtos-public-api */
37 /** @{*/
38 
39 /**
40  * \defgroup rtos_Semaphore Semaphore class
41  * @{
42  */
43 
44 /** The Semaphore class is used to manage and protect access to a set of shared resources.
45  *
46  * @note
47  * Memory considerations: The semaphore control structures will be created on current thread's stack, both for the mbed OS
48  * and underlying RTOS objects (static or dynamic RTOS memory pools are not being used).
49  */
50 class Semaphore : private mbed::NonCopyable<Semaphore> {
51 public:
52  /** Create and Initialize a Semaphore object used for managing resources.
53  @param count number of available resources; maximum index value is (count-1). (default: 0).
54 
55  @note You cannot call this function from ISR context.
56  */
57  Semaphore(int32_t count = 0);
58 
59  /** Create and Initialize a Semaphore object used for managing resources.
60  @param count number of available resources
61  @param max_count maximum number of available resources
62 
63  @note You cannot call this function from ISR context.
64  */
65  Semaphore(int32_t count, uint16_t max_count);
66 
67  /** Wait until a Semaphore resource becomes available.
68 
69  @note You cannot call this function from ISR context.
70  */
71  void acquire();
72 
73  /** Try to acquire a Semaphore resource, and return immediately
74  @return true if a resource was acquired, false otherwise.
75  @note equivalent to try_acquire_for(0)
76 
77  @note You may call this function from ISR context.
78  */
79  bool try_acquire();
80 
81  /** Wait until a Semaphore resource becomes available.
82  @param millisec timeout value.
83  @return true if a resource was acquired, false otherwise.
84 
85  @note You may call this function from ISR context if the millisec parameter is set to 0.
86  @deprecated Pass a chrono duration, not an integer millisecond count. For example use `5s` rather than `5000`.
87  */
88  MBED_DEPRECATED_SINCE("mbed-os-6.0.0", "Pass a chrono duration, not an integer millisecond count. For example use `5s` rather than `5000`.")
89  bool try_acquire_for(uint32_t millisec);
90 
91  /** Wait until a Semaphore resource becomes available.
92  @param rel_time timeout value.
93  @return true if a resource was acquired, false otherwise.
94 
95  @note You may call this function from ISR context if the rel_time parameter is set to 0.
96  */
97  bool try_acquire_for(Kernel::Clock::duration_u32 rel_time);
98 
99  /** Wait until a Semaphore resource becomes available.
100  @param millisec absolute timeout time, referenced to Kernel::get_ms_count()
101  @return true if a resource was acquired, false otherwise.
102  @note the underlying RTOS may have a limit to the maximum wait time
103  due to internal 32-bit computations, but this is guaranteed to work if the
104  wait is <= 0x7fffffff milliseconds (~24 days). If the limit is exceeded,
105  the acquire attempt will time out earlier than specified.
106 
107  @note You cannot call this function from ISR context.
108  @deprecated Pass a chrono time_point, not an integer millisecond count. For example use
109  `Kernel::Clock::now() + 5s` rather than `Kernel::get_ms_count() + 5000`.
110  */
111  MBED_DEPRECATED_SINCE("mbed-os-6.0.0", "Pass a chrono time_point, not an integer millisecond count. For example use `Kernel::Clock::now() + 5s` rather than `Kernel::get_ms_count() + 5000`.")
112  bool try_acquire_until(uint64_t millisec);
113 
114  /** Wait until a Semaphore resource becomes available.
115  @param millisec absolute timeout time, referenced to Kernel::Clock
116  @return true if a resource was acquired, false otherwise.
117  @note the underlying RTOS may have a limit to the maximum wait time
118  due to internal 32-bit computations, but this is guaranteed to work if the
119  wait is <= 0x7fffffff milliseconds (~24 days). If the limit is exceeded,
120  the acquire attempt will time out earlier than specified.
121 
122  @note You cannot call this function from ISR context.
123  */
124  bool try_acquire_until(Kernel::Clock::time_point abs_time);
125 
126  /** Release a Semaphore resource that was obtain with Semaphore::acquire.
127  @return status code that indicates the execution status of the function:
128  @a osOK the token has been correctly released.
129  @a osErrorResource the maximum token count has been reached.
130  @a osErrorParameter internal error.
131 
132  @note You may call this function from ISR context.
133  */
134  osStatus release(void);
135 
136  /** Semaphore destructor
137  *
138  * @note You cannot call this function from ISR context.
139  */
140  ~Semaphore();
141 
142 private:
143  void constructor(int32_t count, uint16_t max_count);
144 
145 #if MBED_CONF_RTOS_PRESENT
146  int32_t _wait(uint32_t millisec);
147 
148  osSemaphoreId_t _id;
149  mbed_rtos_storage_semaphore_t _obj_mem;
150 #else
151  static bool semaphore_available(void *);
152  int32_t _count;
153  uint16_t _max_count;
154 #endif
155 };
156 /** @}*/
157 /** @}*/
158 }
159 #endif
rtos::Semaphore::try_acquire_until
bool try_acquire_until(uint64_t millisec)
Wait until a Semaphore resource becomes available.
rtos::Semaphore::try_acquire_for
bool try_acquire_for(uint32_t millisec)
Wait until a Semaphore resource becomes available.
rtos::Semaphore::release
osStatus release(void)
Release a Semaphore resource that was obtain with Semaphore::acquire.
rtos::Semaphore
The Semaphore class is used to manage and protect access to a set of shared resources.
Definition: Semaphore.h:50
rtos::Semaphore::try_acquire
bool try_acquire()
Try to acquire a Semaphore resource, and return immediately.
mbed::NonCopyable
Prevents generation of copy constructor and copy assignment operator in derived classes.
Definition: NonCopyable.h:162
rtos::Semaphore::Semaphore
Semaphore(int32_t count=0)
Create and Initialize a Semaphore object used for managing resources.
rtos
Definition: TaskBase.h:25
rtos::Semaphore::~Semaphore
~Semaphore()
Semaphore destructor.
rtos::Semaphore::acquire
void acquire()
Wait until a Semaphore resource becomes available.
MBED_DEPRECATED_SINCE
#define MBED_DEPRECATED_SINCE(D, M)
MBED_DEPRECATED("message string") Mark a function declaration as deprecated, if it used then a warnin...
Definition: mbed_toolchain.h:424
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